1. Field of the Invention
The present invention relates generally to multi-hop relay Broadband Wireless Access (BWA) communication system, and in particular, to a method for requesting and allocating upstream bandwidth in a multi-hop Broadband Wireless Access (BWA) communication system.
2. Description of the Related Art
Provisioning of services with diverse Quality of Service (QoS) levels at about 100 Mbps to users is an active study area for a future-generation communication system called a 4th Generation (4G) communication system. Particularly, active research is on going in provisioning of high-speed service by ensuring mobility and QoS to a BWA communication system such as Wireless Local Area Network (WLAN) and Wireless Metropolitan Area Network (WMAN). Major examples are Institute of Electrical and Electronics Engineers (IEEE) 802.16a and IEEE 802.16e.
IEEE 802.16a and IEEE 802.16e communication systems adopt Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access (OFDM/OFDMA) to the physical channels of the WMAN system. IEEE 802.16a considers only a single-cell structure with no regard to mobility of Subscriber Stations (SSs). In contrast, IEEE 802.16e supports the SS′ mobility to the IEEE 802.16a communication system. Hereinafter, a mobile SS is called an MS.
Since signaling is carried out between an MS and a fixed Base Station (BS) via a direct link, a highly reliable radio communication link can be established between them in the typical IEEE 802.16e communication system. However, due to the fixedness of BSs, a wireless network cannot be configured with flexibility. As a result, IEEE 802.16e communication system is not effective in efficiently providing communication services under a radio environment experiencing fluctuating traffic distribution and great change in the number of required calls.
To avert this problem, a multi-hop relay data transmission scheme using fixed Relay Stations (RSs), mobile RSs, or general MSs is used for a general cellular wireless communication system such as IEEE 802.16e. The multi-hop relay wireless communication system can rapidly and advantageously reconfigure a network according to a changed communication environment and enables efficient operation of the whole wireless network. It can expand cell coverage and increase system capacity. If the channel status between a BS and an MS is bad, an RS is installed between them so that the resulting establishment of a multi-hop relay through the RS renders a better radio channel available to the MS. With the use of the multi-hop relay scheme at a cell boundary where the channel status is poor, high-speed data channels become available and the cell coverage is expanded.
In the multi-hop relay BWA communication system, the RSs are infrastructure RSs installed and managed by BSs or client RSs as SSs or MSs, which serve for relay. Also, the RSs can be fixed, nomadic, or mobile like MSs.
Each MS can be allocated an upstream bandwidth by sending a bandwidth request message to a BS via an RS. The RS processes the bandwidth request message between the MS and the BS. Accordingly, there is a need for defining a method for requesting and allocating an upstream bandwidth for the RS.